Routers and other cutting tools are often used with cutting guides that guide the movement of the tool's cutter with respect to a work-piece, such as a piece of wood. For instance, U.S. Pat. No. 4,428,408 for a “Dovetailing Jig” discloses one type of a cutting guide that includes a plurality of moveable guide fingers that provide guide surfaces for facilitating cutting joint elements into work-pieces. The guide fingers interact with a guidebush attached to the cutting tool to guide the movement of the tool's cutter during the cutting procedure. The guidebush may surround the cutter and include an outer guide surface that interacts with surfaces on the guide fingers to guide the cutter's movement. Using these or other types of cutting guide and cutting tool systems helps one accurately and relatively quickly cut a wide variety of joint elements or make other types of cuts in a work-piece, including, but not limited to, box joints, finger joints, dovetail joints (including through, half-blind, and sliding dovetails), and mortise and tenon joints.
Often, it is desirable to adjust the tightness of the fit between joint elements cut using a cutting guide and cutting tool system. Manufacturing variance in cutting guide, guidebush, and cutter dimensions, as well as shaft/bearing wear (“run out”) in the cutting tool, may result in joint elements that fit too loosely or tightly.
One known method for adjusting the fit of a joint is to switch the cutting tool's guidebush for a different guidebush having either a larger or smaller outside diameter, which may result in a tighter or looser fit. Such a method, however, may not allow for precise adjustment of the joint's fit, since the range and increments of adjustment will be limited by the number of guidebushes in the user's possession. Also undesirably, exchanging the guidebush on the cutting tool for a different guidebush may require the removal of the cutter from the cutting tool (such as with dovetail cutters), and could require additional trial and error to reset the correct cutter depth setting.
Another known device and method for adjusting joint fit is disclosed in U.S. Pat. No. 5,584,328 for a “Guidebush Assembly For Use With A Finger Joint Template.” The guidebush disclosed in the '328 patent includes a tapered guide surface, with the lower diameter of the guidebush being smaller than the upper diameter. The guidebush is mounted on a router base in a rotating fashion such that rotating the guidebush in one direction raises it and rotating the guidebush in another direction lowers it. Because the guidebush has a tapered guide surface, raising and lowering the guidebush changes the “effective diameter” of the guidebush (the diameter of the guidebush where it contacts the template), and consequently allows the fit of the joint to be tightened or loosened.
Guidebushes with tapered guide surfaces, such as the guidebushes disclosed in the '328 patent, may be relatively difficult and time-consuming to manufacture.